Metabolism in microbes

Question 1

roles of bacterial organelles:
- anammoxisomes
- thylakoids
- magnetosome
- acidocalisome
- carboxysome
- gas vesicles

Answer 1

anammoxisomes (Planctomycetes) - anaerbic ammonium oxidation
thylakoids (Cyanolbacteria) - photosynthesis
magnetosomes - bacteria align with geomagnetic fields (magnetotaxis)
acidocalicsome - site of polyphosphate and calcium storage
carboxysome - enclose rubisco and carbonic anhydrase, enhancing CO2 fixation
gas vesicles - buoyancy ( move cells up/down a water column)

Question 2

what percentage of microbial species are not readily cultivable?

Answer 2

95-99%
- physiological requirementd are unknown or highly specific
- interdependencies of bacteria require complex mixed culture

Question 3

how do tubeworms in geothermal vents (where there is no sunlight) obtain energy

Answer 3

chemolithautotrophs inside tubeworms, which derive their energy from iron-sulfur compounds that exit the vents
obtain carbon from CO2 (inorganic source) from these vents
produce organic molecules
tubeworms then feed on the bacteria

Question 4

what is delta G dependent on? why is this significant in regards to bacteria?

Answer 4

delta G depends on concentration of components, temperature and pressure
In humans, fairly standard physiochemical system (these conditions stay constant)
In bacteria, due to their high motility they can experience radical changes in conc, pH and temp. They must have highly adaptive systems to respond to these changing conditions

Question 5

ETC in bacteria?

Answer 5

ETC highly homologous to the MT ETC (endosymbiosis)
However, they generate a proton motive force across their plasma membrane

Question 6

why are their more environments where life lives that are anaerobic than aerobic?

Answer 6

oxygen solubility is very low - concentration drops
E.g. need sufficient SA of pond/ pump to ciruclate oxygen or the organisms will die
Conc also drops rapidly in an environment where oxygen is used as the terminal electron acceptor

Question 7

examples of chemolithotrophic electron donors?
(inorganic compounds)

Answer 7

• hydrogen
• sulfur compounds (H2S, elemental sulfur, thiosulfate S2O3^2-)
• ammonia
• nitrite (NO2-)
• iron (Fe2+, FeS2)
• arsentite (III) - H3AsO3

Question 8

terminal electron acceptor for facultative anaerobes?

Answer 8

NO3- or NO2-

Question 9

example of terminal electron acceptors for obligate anaerobes?

include methanogens

Answer 9

Often use SO4^2-, producing H2S
Methanogens (a type of obligate anaerobe uses CO2)
CO2 + 4H2 -> CH4 + 2H2O

Question 10

E’ value of NAD+ /NADH and FAD/FADH

Answer 10

NAD+/NADH = -0.32
FAD/FADH2 = -0.22

Question 11

how do most autotrophs work?

Answer 11

Most autotrophs use the calvin cycle to fix CO2
Alternative pathways are reverse TCA cycle, reductive acetyl-coA pathway, and 3-hydroxypropionate bi-cycle

Reverse TCA cycle - use ATP, add CO2 to make organic molecules

Question 12

ATP and NADPH

Problem encountered by chemolithtrophs?

Answer 12

They still need ATP and NAD(P)H for biosynthesis
- they can generate ATP via PMF
- generating NAD(P)H is tricky because many inorganic electron donors have redox potentials higher than NAD(P)+

Question 13

How do chemolithotrophs overcome the problem they face?

Answer 13

electrons first transerred to CoQ/ cytochrome - enter ETC

1. Forward electron transport
   Electrons flow from donor to acceptor, generating PMF used to make ATP. Received by acceptor
2. Reverse electron transport
   Using energy from PMF to push electrons back through ETC to reduce NAD(P)+
   5x forward pathways to power 1x reverse pathway